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Shed base advice

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Shed base advice

Postby FatboyUK » 21 Mar 2018, 11:47

We are about to move into (hopefully) our last house. The garden isn't huge but big enough for a modest 3.5 x 4m workshop. In an ideal world I would like to put in a full concrete base as recommended by Mike G in his advisory post but access for ready mix or mix my own concrete makes that a bit of an issue when tied in with my recurring back problems (fell off a roof 30 years ago, still paying the price)

I'd thought about setting a grid of suitably treated 100mm posts into postcrete and building a floor frame off of that but I'm concerned about a) longevity of that sort of 'footing', b) the weight loading and c)insulating the floor. What I don't want to do is be lifting the shed off in a few years because its sinking

If I came off the posts with 175mm joists bolted into the posts at 400mm centres leaving a 50mm gap between joist and ground level would I need to close the bottom of the frame off or could I just lay in some 100mm insulation and cover it with osb?

The ground was part of a field originally so I guess I might need to go down a couple of feet?
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Re: Shed base advice

Postby Mike G » 21 Mar 2018, 12:15

There's lots of other ways of building a base other than a concrete slab, albeit that's probably the best solution.

If I were going to do a suspended floor and didn't want much concrete involved, I would possibly look at excavating a narrow trench all round down to some hard ground, filling it with crushed concrete or clean hardcore, whacking that down hard, then laying some concrete lintels or conc. fence posts down on that, bedded in a strong mortar (to aid levelling). You could build up from there in a fairly orthodox way.

That would lift the lowest piece of timber some distance off the ground (lintels would be better than fence posts, because you could get 6" ones, which is about as close to the ground as you want any timber). You then just have to be careful to bring the cladding down just past the top of the concrete so that rainwater run-off dripped clear of the junction between concrete and timber.
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Re: Shed base advice

Postby FatboyUK » 21 Mar 2018, 12:52

Thanks Mike,
Hmm, I'll need to revisit the concrete base I think as this would seriously reduce my headroom.
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Re: Shed base advice

Postby timothyedoran » 21 Mar 2018, 13:02

Form my 3m X 4m workshed. I made some piers by digging down untill I couldn't go deeper, about 60cm. I dug 12 holes 60x60x60cm. Filled with concrete and then built up with concrete blocks.

I had a bad back at that time, so I did it one hole at a time taking my time. I don't have any timbers resting at the floor level.Image

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Re: Shed base advice

Postby Andyp » 21 Mar 2018, 13:28

I watched the guys Building in Alaska on TV using ground screws to support a substantial looking cabin. I saw the piles but missed the episode where they actually screwed them into the ground.

Not sure if there is a DIY solution to screw piling but certainly very Eco-friendly.
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Re: Shed base advice

Postby FatboyUK » 26 Mar 2018, 19:37

Thanks for the different ideas but it looks like I will go for a concrete base after all now that I've found some willing (but not cheap) labour to drive the wheelbarrows! Moving date is now end of june so hopefully I can make a start in July once my beloved has finished with me putting up curtain rails, making wardrobes and the other assorted 'important' things.

One more question while at the planning stage. Electrics: surface run in conduit or cabled like a house in the framing? I'm guessing conduit is best for a wooden building?
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Re: Shed base advice

Postby timothyedoran » 26 Mar 2018, 20:38

I'm going for surface mount in conduit but I'm no expert

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Re: Shed base advice

Postby Malc2098 » 26 Mar 2018, 21:11

Now I'm at the stage of having painted the whole of the inside, I can see that homemade trunking (25x25 and 125mm wide x 11mm OSB) can trunk around the whole 'shop and up to the apex, and therefore will cover up every bit of wiring. I shall used wide plastic box trunking under the ridge apex for the lighting.

I shall use drywall boxes cut into the OSB, and make a join every metre or so, so that I can add more boxes and wiring as necessary.

I never planned this at an early stage, it's just that with left over OSB and 25x50 stock, it occurred to me that it was possible.
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Re: Shed base advice

Postby Andyp » 27 Mar 2018, 07:22

Unless you can be 100% certain that you will never want to change anything around then surface mounting electrics has to be the way to go for a workshop. IMHO.
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Re: Shed base advice

Postby Deejay » 27 Mar 2018, 08:47

Morning FB

I'm guessing conduit is best for a wooden building?

I'd prefer trunking. It's easier to get access to install cables or alter things.

You'll get two 2.5 mm cables in this stuff if you avoid twists ...

https://www.toolstation.com/shop/Electr ... +3m/p42731

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Re: Shed base advice

Postby Phil » 27 Mar 2018, 09:51

Surface mounting.

At the old house I did surface mounting in the workshop and garage.
A lot easier to add new plugs and change the layout.
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Re: Shed base advice

Postby HappyHacker » 27 Mar 2018, 12:12

I found a mix on site concrete supplier who also barrowed the concrete as part of the price, which was very competitive with the normal ready mix suppliers, and you only pay for what you use. There was only one guy doing the barrowing, he was very fit and shifted over 7 cu metres very quickly.
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Re: Shed base advice

Postby FatboyUK » 29 Mar 2018, 08:56

Surface mount is is then. Thanks fellas
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